The present invention relates to a method of preparing metal disulfides of the general formula EQU (Sn.sub.x Me.sub.1-X)S.sub.2,
wherein
Me represents one or more of the elements Ti, Mo, Fe, Cr, Ta, Nb, Mn, Bi, W and Cu, and PA1 x can have values between 0.5 and 1,
and the further processing thereof to form dimetal trisulfides.
Metal sulfides such as SnS.sub.2 are obtained in small amounts by the reaction of the elements in closed vessels at temperatures of 500.degree. C. (G. Brauer, Handbuch der Praparativen Anorganischen Chemie, 3rd Edition, 1978, 2nd Volume, pages 763 to 765). A SnS.sub.2 is also formed by passing hydrogen sulfide into weakly acidic solutions of tin(IV) salts. A tin disulfide, which is also called "mosaic gold", is obtained industrially by heating tin amalgam to red heat with sulfur and NH.sub.4 Cl (Ullmann, Encyklopadie der anorganischen Chemie, 3rd Edition, Volume 24, page 672). On account of its golden color, SnS.sub.2 is used in particular for gilding objects and in painting. Metal disulfides which contain tin are also suitable for use in tribology (e.g. EP 054 616-A1, U.S. Pat. No. 5,098,758, U.S. Pat. No. 5,433,774).
It is known from Gmelin, Handbuch der Anorganischen Chemie, Band Zinn, C2, pages 37 to 40, published by Springer Verlag, 1975, that SnS.sub.2 is obtained by heating amalgamated Sn with excess sulphur and ammonium chloride in open vessels until all the Hg has been expelled (cf. top of page 40). This extract also describes the production of SnS.sub.2 from the elements (Sn and S) in closed vessels under very high pressures (cf. bottom of page 39). Both processes are not suitable for industrial production. The resulting products are consequently also described as preparations which on the one hand still contain 0.01 to 0.1% Hg after sublimation or on the other hand are not completely free from SnS and elemental sulphur.
However, sulfides of this type can only be employed for large-scale industrial use in the field of tribological applications if they can be manufactured inexpensively. It is therefore necessary to provide an inexpensive method which enables large amounts to be produced on an industrial scale.
The object of the present invention is therefore to provide a simple, inexpensive method of preparing tin-containing metal disulfides which does not have the disadvantages of the prior art described above.